Oregon Revised Statutes Revenue and Taxation § 311.662

The validity of any certification, levy, apportionment or collection made pursuant to ORS 291.342, 291.445, 311.375, 311.657 or 311.658 shall not be dependent upon nor be affected by the validity or regularity of any proceeding or procedural activity relating thereto. Any certification required by ORS 291.445 and any transcript pursuant to ORS 311.657 shall contain recitals that they are issued pursuant to ORS 291.342, 291.445, 311.375, 311.657 and 311.658 and such recitals shall be conclusive evidence of their validity and of the regularity of their issuance.